Study of inelastic a p- and dp- scattering in Roper resonance region

A. N. Prokofyev, PNPI 1

Study of inelastic p- and dp- scattering in Roper resonance region

A.N.Prokofyev

Petersburg Nuclear Physics Institute

and SPES4- Collaboration


• Inelastic p- and dp-scattering reactions were studied in the energy region of Roper resonance excitation. Due to the spin and isospin conservation there are only two dominant channels which are open for this reaction: production at the projectile and N* production at the target. A simultaneous registration of the scattered projectile and the secondaries allowed to separate one- and two pions decay of the intermediate state and pick out the 2 channel, which is exclusively connected with the N* baryon intermediate state.

• The shape of the obtained 2 invariant mass spectra was compared with the Oset-Fernandez calculation predictions. It was found that the decay of N* is predominantly going through the spin-isospin scalar state The contribution of the decay through intermediate (N* - N) is small.

• The experiment was carried out at - and d-beams of the Saturne-II accelerator (Saclay). The scattered particles were registered using the SPES4 high resolution spectrometer (projectiles) and wide aperture Forward spectrometer (secondary protons nad pions).


Main Feynman diagrams for p->’N* (dp->d’N*) reaction.

E.Oset, P.Fernandez et al.

•a. isobar excitation at projectile.

•b,c. N* excitation at the target.


The ’ particle spectra for p-inelastic scattering asa function of energy transferred .

Result of the inclusive measurement at Saturne-II -beam.H.P.Morsch et al., PRL 69 (1992) 1326.


SPES4- installation general view(not on scale)


Forward spectrometer of SPES4- installation.(not in scale)

• ST – straw tube hodoscopes

• X, Y, U, V – drift chambers



Spes4-parameters

• SPES4 spectrometer. Nominal acceptance: p/p=5.E-4 This experiment acceptance: p/p=5.E-3

• Forward spectrometer. Angular acceptance: xrad,rad dE/dx resolution – 1 MeV TOF resoluion – 1 nsec Spacial resolution – 0.15 mm p/p ~ 0.03 Missing mass resolution – 20 MeV/c2 Accepted momentum region 0.2 – 1.2 GeV/c


Reaction p

• Four accepted momentum intervals in comparison with the scale of previous inclusive measurement made by H.P.Morsch.


p-reaction

• Missing mass squared spectra for 4 accepted momentum intervals:

• A) secondary protons detected

• B) secondary pions detected



p-reactionManley approach for two-pions decay of Roper resonance

from: E.Hernandez et al.,PRC 65 (2002) 65201

• Feinman diagrams for two main processes contributing to Roper resonance decay into two pions in Manley approach: Diagram amplitude is proportional to (k1.k2).

• a) – intermediate state.

• b) N() – intermediate state


p-reactionManley approach for two-pions decay of Roper resonance

from: E.Hernandez et al., PRC (2002) 65201


p-reactionComparison with Oset-Fernandez predictions

A=(1+c(k1 . k2) )

Form factor and acceptance are included


dp-reaction


dp-reaction


SUMMARY• The p and dp inelastic scattering reactions were exclusively

studied in the energy transfer region corresponded to the Roper resonance excitation region.

• The registration of the scattered projectiles, as well as the charged secondaries allowed to separate different final states, connected with one and two pions production.

• The data in a region, where the Roper resonance production was expected, demonstrate the dominance of the two pion decay of the intermediate N* state . This can be interpreted as the N* (1440 MeV) baryon production. The next possible baryon state D13(1520 Mev) does not fit the data.

• The comparison of the invariant M mass spectra with the theory predictions demonstrates the dominance of the N* decay through the spin, isospin scalar state The contribution of the decay through the Delta resonance is small. This result is in agreement with the data obtained in pp inelastic scattering study at Uppsala.

Documents

Study of inelastic a p- and dp- scattering in Roper resonance region